Boring mill and mechanism to oppose sag in the tool bars thereof



'7 Sheets-Sheet l INVENTOR. pizMjima/gJzz,

A7 TORNEYS Dec. 16, 1947. R. M. SHAW, JR

BORING MILL AND MECHANISM TO OPPOSE SAG IN THE TOOL BARS THEREOF FiledJuly 8', 1943 33 W W R. M. SHAW, JR 2,432,943

BORING MILL AND MECHANISM TO OPPOSE SAG IN THE TOOL BARS THEREOF FiledJuly 8, 1943 7 Sheets-Sheet 2 mm Q . N QNRN gm AN Mwhw Dec. 16, 1947. M.SHAW, JR

v BORING MILL AND MECHANISM TO OPPOSE SAG IN THE TOOL BARS THEREOF 7Sheets-Sheet 3 Filed July 8, 1943 INVENTOR:

1267/ ii/ILS/ZHMJ BY 0% e- ATTORNEYS.

Dec. 16, 1947. R. M. SHAW, JR

BORING MILL AND MECHANISM TO OPPOSE SAG IN THE TOOL BARS THEREOF FiledJuly a, 1943 7 Sheets-Shefc 4 0 BY H Dec. 16, 1947.

R. M. SHAW, JR

BORING MILL AND MECHANISM TO OPPOSE SAG IN.THE' TOOL BARS THEREOF FiledJuly s, 1943 7 Sheets-Sheet s FJGL 5.

61 6f 63 47 61 y vgzvi W I TNESSES; 15 r/wzi fiwd A TTORNEYS.

Dec. 16, 1947.

R. M. SHAW, JR

BORING MILL AND MECHANISM TO OPPOSE SAG IN THE TOOL BARS THEREOF FiledJuly 8, 1945 7 Sheets-Sheet 6 INVENTOR; Bozo/2M -512 aw, J1.

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Dec. 16, 1947. R. M. SHAW, JR 2,432.943

BORING MILL AND MECHANISM TO OPPOSE SAG IN THE TOOL BARS THEREOF FiledJuly 8, 1943 7 Sheets-Sheet '7 o m q L wt 7 Q WITNESSES: INVENTOR:

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BY M f ATTORNEYS.

Patented Dec. 16, 1947 BORING MILL AND MECHANISM TO OPPOSE SAG IN THETOOL BARS THEREOF Ralph M. Shaw, Jr., Edgewater Park, N. J., as-

signor to Pedrick Tool & Machine Company, Philadelphia, Pa., acorporation of Pennsylvania Application July 8, 1943, Serial No. 493,823

11 Claims.

This invention is concerned with boring mills and also has to do Withimproved mechanism to oppose sag in the tool bars thereof.

With mills of the two-column types ordinarily used heretofore for boringoperations, difficulty was had in keeping the bore true, particularly inmachining relatively long objects such for example as gun barrels, dueto the sagging of the bar or shaft along which the cutter head travelsbetween the columns during the boring. Thus in these old forms of boringmills the span between the columns and hence the length of the tubeswhich could be cut was limited by the degree of permissible sag of thetool shaft, the maximum length of allowable span for a 6 inch tool barfor example in existing mills being approximately 12 feet. To eliminateor minimize sag, various expedients have been heretofore resorted to,such as employing tubular bars or shafts instead of bars or shafts ofsolid cross section to reduce weight; solidly anchoring the ends of thebars or shafts; providing tiedowns in the form of drawing mechanisms inthe plane of the bearings for the bar or shaft; or to have followersmove along with the cutting tools in snug engagement with the previouslycut portions of the bores to hold the bars centered. The first twomentioned of these prior art schemes could not be relied upon foraccuracy, and the last mentioned was objectionable because of thedifficulty in disposing of the metal trimmings carried along by thefollowers withouout attendant scratching or scoring of the machinedsurface.

The chief aims of my invention are to overcome the above drawbacks andto enable true and accurate boring along absolutely straight lines ofobjects of much greater length than possible heretofore. Theseobjectives I realize as hereinafter more fully set forth byprogressively flexing the tool bar or shaft in such a way as tocompensate for variant sag of the span of said bar or shaft betweensupports or bearings and along which the cutting tool is advanced duringthe boring; and through the further provision of an improved boring millwhich is characterized by having three bearing columns instead of two asin conventional prior art mills, and in which is incorporatedregulatable mechanism for progressively flexing the tool bar or shaft atone of the end columns and for concurrently controlling the rate oftravel of the tool along the portion of the bar or shaft within the workbeing machined and spanned between the other two columns, throughout theboring period for attainment of the desideratum above pointed out.

In connection with a boring mill having the foregoing attributes, I aimto enable, through provision of simple and reliable mechanism such asalso hereinafter more fully disclosed, rapid adjustment of the columnsrelative to each other as well as vertical adjustment of the bearingsfor the tool bar or shaft, either independently or collectively inadapting the mill to accommodate for operation upon objects of difierentlength and/ or diameter, and also to enable certain of the columns to beshifted on the mill bed relative to others during the boring underdifferent conditions of use of the mill.

Other objects and attendant advantages will appear from the followingdetailed description of the attached drawings, wherein Fig. 1 is afragmentary broken-out view in side elevation of a boring millconveniently embodying my invention in one form.

Figs. 2 and 3 are fragmentary horizontal sectional views taken asindicated respectively by the angled arrows II--II and IIIIII in Fig. 1.

Fig. 4 is a cross sectional view taken as indicated by the angled arrowsIV-IV in Figs. 13.

Fig. 5 is a vertical sectional View taken as indicated by the angledarrows V--V in Figs. 2-4.

Fig. 6 is a fragmentary detail sectional view taken as indicated by theangled arrows VI-VI in Fig. 5.

Fig. 'l is a detail cross sectional view taken as indicated by theangled arrows VIIVII in Fig. 1.

Fig. 8 is a detail view in axial section of a commutator switchassociated with the electric drive means of the mill.

Figs. 9, l0 and 11 are diagrammatic views showing successive stages orphases in the method of boring according to my invention.

Figs. 12 and 13 are views in side elevation generally like Fig. l but ona smaller scale showing two alternative embodiments of my invention.

With more detailed reference first to Figs. 1-8, the form of my improvedmill therein illustrated has an elongate bed IS with laterally-spacedlongitudinally-extending parallel track rails [6 of Tcross section whichare connected at their bottoms by a base web IT. Shiftably mounted onthe bed l5 are three columns which are respectively designated by thecharacters l8, Illa and l8b. Except as hereinafter particularly pointedout, these columns are identical both as regards their design and theappurtenances associated with them, and therefore the description whichis about to follow of the column I8 will also serve for the columns [8aand lb. From Figs. 2 and 4 it will be noted that the column l8 is in theform of an open vertically oblong frame with side members I9, an uppertransverse member 20, and a lower transverse member 2|, the

latter having gibs 22 at opposite ends thereof which underreach theoutside flanges of the track rails I6.

Guided for up and down adjustment within the opening of the column i8 isa cross head 25 with a hollow central boss 26 which houses a self-aligning spherical roller bearing21 forthe horizontal tool bar or shaft28 of the mill, the inner race of said ball bearing being secured tosaidshaft in abutting relation to a shoulder 26a: thereon as shown in Fig.2. Confined againstaxial movement within a recessed projection'29 (Figs.2 and at one side of the boss 26 of the cross head is a worm wheel 30which is rotatable about and which threadedly engages a vertical screwspindle 3| whereof the ends are. suitably journaled in ball bearings 32and 33 at the upper and lower transversemembers 20 andi2l ,ofthecolumnl8, see Figs. 2, 5 and 6. The worm'wheel '30 is operable by means of anintermeshing worm 34 affixed to a' shaft35 which is provided with ahandwheel 36, and which is. journaled adjacent its opposite ends in bearings31 and-38 (Figs; 2 and 6). As shown the bearing 31 is pivoted to swinglaterally about vertical axis studs 39 in a clevis 40 at the front ofthe projection 29,-while the bearing 38 is normally seated in, anotherclevis 4| on said projection with the worm 34 normally engaging the wormwheel 30. A retractible keeper pin 42 serves as a means to lock'thebearing 38 within the clevis 4 Thus through thearrangement justdescribed it is possible to vertically adjust the head 25 within thecolumn l8 thereby to raise or lower the tool shaft 28 in accordance withthe direction in'which'the hand wheel 36 is turned. By means ofmanuallyoperable screws 43 bearing on clamp shoes 44 lodged within thegrooves 45- at oppositeends of the cross head 25 and engaging verticalguide flanges 46 centrally of the side members 19 of the column I8, saidcross head is securable against accidental displacement afteradjustment.

Pendent fromjthe lower transverse member 2| of the column I8 is adouble-chambered housing 41 which is formed by pairs oflaterally-spaced, opposingly-arranged crosswise channel pieces 48 and 49and a bottom plate50. As best seen in Figs. 4 and 5,'the vertical screwspindle 3| extends down into one of'the sub-divisions of the housing 41and is'there sustained at that end by the ball bearing 33. Secured tothespindle 3| immediately above the bearing 33 is a spiral gear wheel 5 I-that mates with a similar wheel 52 (Figs. 3 and 4) on a horizontal shaft53 which extends longitudinally of'the mill substantially throughout thelength of the, bed l3 and is journaled in bearings 55, on the sidechannels 48 of the housing 47. Asshown in Fig. 3, the spiral gear 52 isconfined between ball thrust bearings 56, and within its bore is a key5! which slidingly engages a lengthwise groove 58 in the shaft 53.Extending parallel with the shaft 53 likewise substantiallythroughout'the length ofthe bed I5 is a screw spindle 66 whichis'slmilarly journaled in bearings 6| on the side channels '49 of thehousing '41, and whereon is, mounted betweenthrust bearings 62 withinthe. other sub-division of said housing 41, an internally-threadedinter-engaging worm wheel63. 'Arranged to cooperate with the worm wheel63 is a worm 64 on a crosswise arranged shaft 65 which latter isjournaled in bearings 66 and 61 on the transverse lower member 2| of thecolumn and which extends outward through a vertical slot 68 in one ofthe side members [9 of said column, being provided at its protruding endwith a hand wheel 69. The worm 64 is normally in mesh with the wormwheel 33, as shown, so that by turning the hand wheel 69 in onedirection or another,-the column l8 can be shifted forward or backwardalong the bed [5. In order that the worm 64 may be lifted out of contactwith the worm wheel 63 for a purpose also later on explained, the innerbearing 66 of the shaft 65 is pivotally connected by horizontal axisscrew studs 16 in a clevised bracket H on the lower transverse member 2|of the column l8, while the outer bearing 61 is lodged in a secondclevised bracket 12 on said cross member being normally locked thereinby a, retractible keeper pin 13. By means of manually-operable clampscrews indicated at 15 the column I8 can be secured against accidentaldisplacement in adjusted positions on the bed- I5.

Since a worm gear can be driven by the worm but not by the wheel, theuse of such gears in connection with various manual adjustments abovedescribed is advantageous since when the worms and the wheels are placedin mesh, the wheels are locked against turning for movement of thecolumns or bearing heads as the case may be, by the horizontal andvertical screw spindles respectively.

All of the appurtenances thus far described as being associated with thecolumn [8 are duplicated in columns |8a and I82), and in the latteridentified by the same reference numerals previously employed withassociation however of the letters a and b respectively for convenienceof ready distinction. The columns |8a and |8b are thus identical withthe column l8 except for being of lessheight as will be noted from Fig.l, and in that the inner races of the bearings 21a and 271) are slidablymounted on the tool shaft 28.

As shown in Fig. 3, spur pinions l6 and T! are secured respectivelytothe left-hand ends of the longitudinal shaft 53 and the parallelspindle 60, these pinions being in mesh with a driving spur wheel 18 onthe output shaft 19 of a variable speed-reducing unit 80, which, and anelectric driving motor 8| therefor, are supported on the base plate I!of the 'bed.

Mounted on the-bed l5 between the columns |8a and IS?) with capacity forbeing independently shifted along the rails I6 is a carriage 82 (Fig. 1)with a pedestal 83 thereon for supporting a tube T or the like which isto be bored, said pedestal being transversely-adjustable by means of ascrew 84 and having a dovetail guide connection at 85 with saidcarriage.

The cutting means herein shown by way of example includes a head 86*which carries four radially-arranged cutting tools 81 ,and which isshiftable along the tool bar-or shaft 28 by means of anindependently-rotatable feed screw 88 occuplying a longitudinal recess89 in said shaft, see Figs. 4 and 7 also. From Fig. 2 it will be notedthat adjacent its left hand end the feed screw 88 is formed with aplurality of spaced thrust collars 88m which are engaged in a thrustbearing 68y recessed laterally into the tool bar or shaft 28. As aconsequence of this arrangement, during the boring, the thrust of thefeed screw 88 is transmitted to the bar 28 and by the latter to thecolumn. 8'through the roller thrust bearing .27. The tool bar or'shaft28 is rotated hr u h a pu r .9ilthereon (Figs. 1. and 4) in mesh withadriving pinion 9| on the shaft I of an electric motor 92 which ismounted on the cross head 25. The feed screw 88 is, on the other hand,rotated, through speed-reduction gearing generally designated 93, by avariable-speed electric motor 96 affixed to the spur gear 99 andsupplied with electric current through a conductor cable 94. Twisting ofthe cable 94 as the motor 96 rotates bodily with the gear wheel 99 isprevented through interposition of a commutator switch which isseparately illustrated in Fig. 8 and generally designated by the numeral91. As shown, the commutator switch 91 has its annular housing 98secured to the casing of the motor 96 by brackets 99, Within the housing93 is a non-revolving disk I99 of insulation which carries a pluralityof spring-pressed brushes WI (the number corresponding with that of theconductors in the cable 94 and the type of motor 96 employed), and whichhas its periphery engaged with a working fit in an annular groove I92 ofsaid housing, said disk being additionally supported at its axis by ascrew stud I93 taken into the housing of said motor. The brushes I9!frictionally bear against contact rings I95 embedded in another disk I96of insulation which is fixedly secured to and closes the housing 98 atthe inner side of the latter. The taps shown at I91 are for individualconnection of the leads (not shown) from the internal wiring of themotor 96.

To prepare the mill for operation, the bearings 26, 26a, 26b are firstvertically adjusted in the columns I8, IBa, I8b approximately to thelevel which the tube to be machined will occupy during the boring, andthe spindle 88 is rotated to bring the tool head 86 to a positionclosely adjacent the column I8a. Column I817 is then shifted rightwardon the bed I5 until the corresponding end of the tool bar 28 is clearedand column I80. either at the same time or later shifted to the right orleft as may be required, whereupon the tube is applied over said bar andsupported on pedestal 93. If more convenient from the standpoint of theprevious setting, the last described step can be carried out by backingoff the column I8 to draw the bar 28 through the bearing 28a of columnIBa, and out of the bearing 26?) of column [8b until its end issufiiciently cleared for application of the tube. With the tube properlyplaced, column I9?) is shifted reversely on the bed I5 to re-engage theright-hand end of the bar 28 within its bearing 2% after which thebearings 26a and 251) are again vertically adjusted until all of themaccurately center in the axis of the tube. Following this, column I8 isshifted on the bed I5 relative to the column I8a until spaced by adefinite distance proportionate to the length of the tube T. Theshifting of the columns I8, Mia and I 8?) can ordinarily be rapidlyeifected under power by means of the reversible motor 8! by bringing theworms 64, 64a, 94b associated with them individually into mesh with theworm wheels 63, 63a, 631) on the screw spindle 69 as required. After thecolumn I8 has been so shifted, the corresponding worm 88 is disengagedfrom the associated worm wheel 63 so that the latter can rotate with thescrew spindle 69 with out causing further movement of said column. Asimilar procedure is thereupon resorted to in connection with the worms84a and 64b in order to shift the columns I8a and I81) as may benecessary or desired. The initial vertical adjustment of the bearings28, 26a, 26b in the columns I8, I8a, I8!) is likewise ordinarilyeffected rapidly under power by means of the motor 8| which through thehorizontal shaft 53 actuates the inter-geared vertical screw spindles3|, 3m, 3Ib in the columns I8, I8a, IS!) in one direction or the otheras required by selectively meshing the worms 34, 34a, 341) with the wormwheels 39, 39a, 39b respectively. With this accomplished, the Worms 39,34a and 34b are retracted from the wheels 39, 39a and 39b and the motor8| stopped. Then if finer adjustment of the columns I8, I8 or I8b or ofthe bearings 26, 26a, 2% should be necessary, this is effected byre-engaging the Worms 64, 64a, 642) with the wheels 63, 63a, 83b, andthe worms 34, 34a, 34b with the wheels 39, 39a, 39b, and operating themmanually. After final adjustment of the parts as just explained, theworms 64, 64a, 641) are again retracted and the clamp screws (5tightened to fix the columns I8, I8a, I8b against accidental shiftingduring the boring operation. The worms 34a, 341) are likewise againwithdrawn from the worm wheels 39a, 39b, but the worm 34 is left in meshwith the wheel 39 so that the vertical screw spindle 3| may be drivensubsequently under power as the boring proceeds for a reason presentlydisclosed. The set-up after these preparatory steps are completed willbe in accordance with the diagram of Fig. 9 with the span of the toolshaft 28 sagging as exaggeratedly shown between the columns I8a and I8b.

All being now in readiness, the mill is operated in the followingmanner: The motor 92 is first started to rotate the tool shaft 28;whereupon the motors 8I and 96 are simultaneously set into motion, themotor 8| to drive the horizontal shaft 53 and the horizontal spindle 69in the bed I5 (said spindle rotating idly in the resent instance duringthe boring), the motor 96 being started to drive the feed screw 88 insaid tool shaft. As a consequence. the tool head 86 is advancedrightward along the tool shaft 28 within the tube T and the bearing 28concurrently depressed gradually in the column I8 by action of thevertical screw spindle 3| upon the locked worm wheel 39 on the head 25to progressively flex the end of the shaft 28 beyond the column IBa. Asa result the span of the shaft between said column and the column I8b iscaused to assume a compound or sinuous curvature as exaggeratedly shownin Fig. 10 and the node of the curve to travel from left to right in theaxis of the tube T. Now if the speed of the drive of the cutter head 86is adjusted to move said head rightward at the same rate whilemaintained at the node of the curve, its travel will also be confined tothe axis of the tube T and thus cut a bore which will be absolutelystraight and true. Upon maximum depression of the bearing 26 in thecolumn I8, the curvature of the span of the shaft 28 will assume anupward or negative catenary sag as shown in Fig. 11. when the cutterhead 86 will have reached the far end of the tube T and completed theboring. In practice, it is of course essential that the extent and rateof lowering of the bearing 2611 be accurately predeterminedmathematically in accordance with the length of the span of the toolshaft between the columns l8a and I81), and the variable speed drive 89associated with the motor 8| set to maintain it. The shaft 28 submitsreadily to being bent and strained as described without binding byreason of being journaled in the selfaligning spherical bearings 21, 21aand 21b in the cross heads of the respective columns I8, 18a and I81).Thus, through my invention, it is possible to accurately machine muchlonger tubes than .can be done withboring-mills of'rtheordinarytypes'heretofore available. Itis to-.-be..particularly noted that duringthe boring the thrust ofthettool head 86 is transmitted by the feedscrew.'through the thrust bearing BSyftQ the. bar or shaft 28, and bytheilatter, through its shoulder-28.7: to the roller bearing 21 in thecolumn 18, so that none of such thrust isicommunicated to the drivemechanism for'the feed.. This is a distinct advantage over: prioraartmills wherein the toolbar or shaft is slidable in all the columns andthe thrust communicated to the feed mechanism; with causation ofv severestrains therein and rapid wear of its parts.

Another way in which the mill can be employed is illustrated in Fig. 12where an 'additionalcutting tool head 86c is made fast tothe-shaft 28 asby a set screw I Hi. In this case after the bearings :26, 26a, 2611 havebeenproperlyadjusted, the worms 34, 34a and 34b arev withdrawn andthe-clamp screws 43 tightened to prevent-subsequent displacement of Ithe heads 25, 125a, 25b and'hence of the bearings 2516a, 26?). The-motor98 is thereupon started andthe boring in :this instance effected withoutflexure of the "shaft 28-. In addition, the hand wheel shaftfi=associated with the column Illa is locked inelevatedinoperativeposition to prevent shifting of said'column on the bed [5 by the screwspindle=6ll .and said column secured in the positionin which it isshown. The columns 18 and 18b, on=theother hand, are coupled with thescrew spindle-fiB-so as to be concurrently advanced on the bed when themotor 8! is started.- Assuming such ad- Vance to be as indicated by thearrows on the .columns l8 and 8b in Fig. 12, thetool shaft 28 will bebodily shifted axially and slide in-the cross head of the column Eta. Asa consequence; it will be seen that the cutter head .860 will headvancedfrom right to left in the tube T, while the cutter head 86 will beconcurrently advanced in the opposite direction by the feed screw 88,the latter being of course rotated in the proper direction by the motor98 to bring this about, and.- the speed of said motor being set tocause" the head .86 to be advanced at such a rate with respectzto theaxial shifting of the shaft 28 that thetwo heads will eventually meetmid-way of the length of said tube. Duplex boring in this way willobviously be more rapid than by the first describeduse of the press andcan be resorted to whenever 'thecharacter of the work will permit it.

Fig. 13 shows a modified-arrangement invwhich the end portions of thefeed shafti83-are1oppositely-threaded as at 38erand 88f'toact'respectively on the cutter heads 85c and 86]. Ashin the firstdescribed instance, the columns l8-,l8a and I81) are all securedagainstrshifting on the bed after having been properlypositioned withrelation to the tube T which is tobemaohined, and the boring effectedsimply by rotationof the feed screw 88. Due ,to the reverselyi-pitchedthreads of the feed screw'88, itwillbe apparent that as the latter isdifferentially rotated in respect to the shaft 28, the cutterheads BEeand-85f will gradually approach each :otherwun-til'they eventually meetmid-way of the. length :of the tube T As in the case of the apparatusofrFig. 12, the boring is effected without flexureiof 'the shaft.

Having thus described my invention, I claim:

1. In a boring mill, 2, pair of spaced columns; means for horizontallysupporting a'tube' which is to'be bored in the intervalbetweenisaidcolumns;

a-tool shaft supportedaxially'withinrthe :tubetby bearings'on saidcolumns with one end projecting beyondone of the columns; a third columnwith a vertically-movable bearing in which the projecting-end of theshaft is engaged; and means for moving the bearing in said third columnto variantly flex the projecting end of the shaft and so compensate forsagging of that portion of the shaft within the tube as the tool isadvanced therealong.

2; A'boring mill according to claim 1, in which the bearings on allthree columns are of a sphericaltype to facilitate-flexing of the shaft.

3. In a boring mill, a pair of columns; a supportfor a tube disposedbetween the two columns; a cutter tool shaft; bearings on said column inwhich the shaft is slidable endwise; a third column with a thrustbearing thereon in which an outboard end of the shaft is fixed againstendwise sliding; a bed on which the columns are supported; and means forshifting said third column along the bed relative to the firsttwo-columns to insert the shaft into or to withdraw it from the tube.

4. A boringmill characterized as in claim 3, further including meanswhereby the two columns first mentioned can be shifted along the bedindependently of each other and of the third column.

- 5. A boring mill characterized as in claim 3, further including a feedscrew for shifting the tool along the shaft during the boring; and meanson the shaft for taking the thrust of the feed screw.

- 6. A boring mill characterized as in claim 3, in which:the bearings ofthe two columns first mentioned are spherical; and further includingmeans for'progressively moving the thrust bearingin the third columnvertically to flex the outboard end of the shaft in order to compensatefor the Weightof the tool in its travel along. said shaft andmaintaining it coaxial with the tube during the boring.

7. A boring mill characterized as in claim 3, further including meanswhereby the bearings in the respective columns can be simultaneouslyadjusted Vertically to initially center the tool shaft within the tube.

8. Aboring mill characterized as in claim 3 wherein the column shiftingmeans includes a rotary-screw spindle which-extends longitudinally ofthe bed, nut means for engaging the screw spindle-held against aXialmovement on: therespective columns, and means whereby said nut means canbe independently locked against rotation when the corresponding columnsare to'be shifted.

9;-.A.boring mill characterized as in claim 3, wherein the bearings ofthe two columns first mentioned are spherical; and further includingpower means on the third column for progressively advancing the cuttingtool along the shaft during the boring and at the same timeprogressively moving the-thrust bearing vertically to flex-the outboardend of the shaft in order to compensate for the weight of the tool as itis moved'along and thereby maintaining it coaxial within the tube.

.10; In a boring mill, a-pair of columns; a support: for a-tube disposedbetween the two columns; a cutter .tool shaft; bearings on said columnsin .which theshaft is slidable 'endwise; a third column with a thrustbearing thereon in which an outboard: end of the shaft is held againstendwise sliding; a bed on which the columns are supported; a cuttingtool secured to the shaft; a

9 second cutting tool capable of being advanced along the shaft; meansfor moving the third column relative to the other two on the bed toshift the shaft and thereby cause the fixed tool to travel lengthwise ofthe tube during the boring; and means for concurrently advancing themovable tool along the shaft in the opposite direction.

11. In a, boring mill, a pair of spaced columns;

means for supporting a tube or the like to be bored, in the intervalbetween said columns; spherical bearings in the respective columns; ashaft rotative in the bearings and projecting beyond one of them; acutting tool movable along the shaft; and means for variantly flexingthe projecting end of the shaft to compensate for sagging in the portionthereof between the columns as the tool is advanced therealong.

RALPH M. SHAW, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number Number UNITED STATES PATENTS Name Date MacDonald Oct. 21, 1873Julien June 12, 1888 Richards Jan. '7, 1890 Taylor May 27, 1890 OtisAug. 9, 1904 Rowe June 20, 1911 Greven Oct. 31, 1922 Pedrick Apr. 15,1924 Jeschor Aug. 22, 1939 Snyder Apr. 6, 1943 Arter May 1, 1945 WernerAug. 28, 1945 FOREIGN PATENTS Country Date Germany May 1, 1911 GermanyMay 5, 1911

